1. Field of the Invention
The present invention relates to an actuator drive control device for an active vibration isolation support system, in which a control apparatus controls an operation of an actuator based on a vibration state of an engine which is estimated from angular acceleration of a crankshaft, so as to suppress transmission of vibration from an engine.
2. Description of the Related Art
Such an active vibration isolation support system is known from Japanese Patent Laid-open No. 2003-113892.
This active vibration isolation support system, described in the reference, calculates a crank angular speed from a time interval of crank pulses which are outputted at each predetermined rotational angle of the crankshaft; calculates torque of the crankshaft from a crank angular acceleration obtained by differentiating the crank angular speed with respect to time; estimates the vibration state of the engine as a variation amount of torque; and controls application of electrical current to a coil of an actuator in accordance with the vibration state of the engine, to effect the vibration isolation function.
FIG. 8A shows a variation waveform of the crank angular speed in the case where an engine rotational speed Ne is substantially constant. The variation waveform of the crank angular speed is in a sine wave shape, the angular acceleration of the crankshaft can be approximated at a value 2ω/T which is obtained by dividing a variation amount Δω by a half of one period T. Accordingly, based on the difference between “+2ω/T” that is a positive crank angular acceleration in the one period of the variation waveform of the crank angular speed and “−2ω/T” that is a negative crank angular acceleration, the torque variation of the crankshaft, namely, the vibration state of the engine can be estimated.
In the example shown in FIG. 8A, the engine rotational speed Ne is substantially constant, but when the conventional method is applied to the case where the engine rotational speed Ne increases or decreases, the following problem occurs.
FIG. 8B shows a variation waveform of the crank angular speed in the case where the engine rotational speed Ne increases. In this case, the regular variation amount Δω of the crank angular speed should be measured in the direction orthogonal to the straight line representing the engine rotational speed Ne, but actually a variation amount Δω′ in the direction parallel to the vertical axis is measured, so that the variation amount Δω′ becomes smaller than the regular variation amount Δω. Accordingly, an error disadvantageously occurs when the vibration state of the engine is estimated based on the variation amount Δω′ in the direction parallel to the vertical axis. This problem also occurs in the case where the engine rotational speed Ne decreases.
The present invention has been achieved under the above-mentioned circumstances, and has an object to accurately estimate a vibration state of an engine when an engine rotational speed increases and decreases, thereby precisely controlling an active vibration isolation support system.